For example, in the machine tool such as an NC lathe, a machine operation check is performed by an operator according to a sequence program. At that time, a ladder diagram screen is displayed on the operation panel of the machine tool, and ON/OFF switching of a contact point is performed. Meanwhile, since confirmation of an output state that occurs due to switching in this manner is necessary, the operator performs confirmation by switching the display of the operation panel to an I/O monitor screen.